1. Field of the Invention
The present invention relates to improvements in or to a rangefinder device and a camera which can measure distances based on both an active method and on a passive method.
2. Description of the Related Art
As a rangefinder device provided in a conventional camera, there has been proposed a rangefinder device by Japanese Patent Publication (KOKOKU) No. 5-22843, which uses a so-called active method, and is constructed such that the camera flashes or projects a subject, and when integrating the reflected light, a pair of CCDs arranged like a ring cycle accumulated charges, while a charge rejecting means (hereinafter referred to as xe2x80x9cthe skim meansxe2x80x9d) rejects a fixed amount of charges of extraneous-light components other than reflected light by the projection, and the distance to the subject is determined based on the relative value of the receiving position of the reflected light from the subject, using signals from the pair of CCDS.
Another rangefinder device of this kind has been proposed by Japanese Laid-Open Patent Publication (KOKAI) No. 9-196665, which can measure the distance based not only on the active method but also on a passive method using only extraneous light, by turning off the projection and stopping the operation of the skim means.
The above described autofocus optical system is generally provided on an optical axis different from the photographic optical system or the finder optical system. With such a camera, if the focal distance of the taking lens is changed, the ranging frame in the finder deviates from the actual ranging area. In such a case, if the distance is measured according to the passive method with a main subject present within the ranging frame and with an object present outside the ranging frame, the object being at a different distance from the main subject, the result of the distance measurement is affected by the object located outside the main subject. That is, a so-called conflict between far and near objects may occur.
Thus, Japanese Laid-Open Patent Publication (KOKAI) No. 2-293833 has proposed a camera which executes ranging calculations using only a part of pixel data that corresponds to the ranging frame out of the actual ranging area, depending on the focal distance.
However, with the rangefinder device that can use both the active and passive methods (hereinafter referred to as xe2x80x9cthe hybrid rangefinder devicexe2x80x9d) as disclosed in Japanese Laid-Open Patent Publication (KOKAI) No. 9-196665, if such control as proposed by Japanese Laid-Open Patent Publication (KOKAI) No. 2-293833 is executed, a sensor for use in a ranging operation has a reduced light receiving area on a long focal distance side. Thus, the active method can only deal with a reduced range of distances to which the camera can be adapted, thus making it impossible to carry out measurement of the distance to a subject located at a short distance. This phenomenon will be described with reference to FIG. 10.
In FIG. 10, reference numerals 201 and 202 denote a first light receiving element CCD (L) and a second light receiving element CCD (R), respectively. Reference numerals 203 and 204 denote light receiving lenses with their principal points arranged at a fixed interval (baseline length) B. Reference numeral 205 denotes an infrared light emitting diode (hereinafter referred to as xe2x80x9cthe IREDxe2x80x9d) as a projecting element, and reference numeral 206 denotes a projecting lens. The IRED 205 and the projecting lens 206 form projecting means. Reference numeral 207 denotes a subject.
In the figure, the distance from the principal points of the light receiving lenses 203, 204 to the CCD 201, 202 is defined as f, and the distance from the principal points of the light receiving lenses 203, 204 to the subject 207 is defined as H. The interval (baseline length) between the principal points of the light receiving lenses 203 and 204 is defined as B, and the interval between the principal points of the projecting lenses 206 and the light receiving lens 203 is defined as K.
Further, assuming that the distance by which a received light image moves from a central position of reflected light observed when the subject 207 is located at a point at infinity and if reflected light therefrom is collected by the light receiving lens 203 and then formed into an image on the CCD 201, to a central position of reflected light observed when the subject 207 is located at the above distance H and if reflected light therefrom is collected by the light receiving lens 203 and then formed into an image on the CCD 201 is defined as X1, and the distance by which the received light image moves from a central position of reflected light observed when the subject 207 is located at the point at infinity and if reflected light therefrom is collected by the light receiving lens 204 and then formed into an image on the CCD 202, to a central position of reflected light observed when the subject 207 is located at the above distance H and if reflected light therefrom is collected by the light receiving lens 204 and then formed into an image on the CCD 202 is defined as X2, the following relationship is established:
H=(Bxc3x97f)/(X2xe2x88x92X1)xe2x80x83xe2x80x83(1)
By determining the denominator (X2xe2x88x92X1) on the right side of the above Equation (1) using the known phase difference detecting method, the distance to the subject 207 can be calculated.
Here, the distances by which the received light images move on the CCD 201 and the CCD 202 will be explained.
The distance X1 by which the image moves on the CCD 201 is given by:
X1=(Kxc3x97f)/H
The distance X2 by which the image moves on the CCD 202 is given by:
X2={(K+B)xc3x97f}/H
Accordingly, as the light receiving areas of the CCD 201 and the CCD 202 are shorter, the moving distances X1 and X2 increase when the distance H to the subject is short, resulting in that the received light images fall out of the light receiving areas of the CCD 201 and CCD 202. Therefore, to enable measurement of the distance H to the subject over a large range, that is, from a far distance to a close distance, the light receiving areas of the CCD 201 and the CCD 202 have to be sufficiently large.
It is an object of the present invention to provide a rangefinder device and a camera which, in measuring a distance by the active method, are capable of properly measuring the distance even if the object to be measured is located at a short distance, while in measuring a distance by the passive method, are capable of measuring the distance without causing the conflict between far and near objects.
It is another object of the present invention to provide a rangefinder device and a camera which are capable of obtaining highly accurate distance measurement information from both results of the distance measurements executed according to the active method and the passive method.
To attain the above objects, the present invention provides a rangefinder device comprising a projecting section that projects spot-shaped light on a range-finding object, a light receiving section comprising a plurality of photoelectric converting elements, a first calculating section that calculates distance measurement information based on an output from the light receiving section receiving reflected light from the range-finding object, by driving the projecting section to project the light, and a second calculating section that calculates distance measurement information based on an output from the light receiving section receiving extraneous light reflected from the range-finding object, without driving the projecting section, and a control section that sets a light receiving range of the light receiving section used for calculation of the distance measurement information by the second calculating section to be narrower than a light receiving range of the light receiving section used for calculation of the distance measurement information by the first calculating section.
Preferably, the projecting section projects light in a plurality of different directions, and the light receiving section comprises a plurality of light receiving sections disposed to receive respective corresponding lights obtained when light projected in the plurality of different directions is reflected by the range-finding object, and the control section sets a light receiving range of the plurality of light receiving sections used for calculation of the distance measurement information by the second calculating section to be narrower than a light receiving range of plurality of light receiving sections used for calculation of the distance measurement information by the first calculating section.
More preferably, the rangefinder device according to the present invention comprises a third calculating section that calculates final distance measurement information based on the distance measurement information obtained by the first calculating section and the distance measurement information obtained by the second calculating section.
To attain the above objects, the present invention also provides a camera comprising a projecting section that projects spot-shaped light on a subject, a light receiving section comprising a plurality of photoelectric converting elements, a first calculating section that calculates distance measurement information based on an output from the light receiving section receiving reflected light from the subject, by driving the projecting section to project the light, and a second calculating section that calculates distance measurement information based on an output from the light receiving section receiving extraneous light reflected from the subject without driving the projecting section, and a control section that sets a light receiving range of the light receiving section used for calculation of the distance measurement information by the second calculating section to be narrower than a light receiving range of the light receiving section used for calculation of the distance measurement information by the first calculating section.
Preferably, the projecting section projects light in a plurality of different directions, and the light receiving section comprises a plurality of light receiving sections disposed to receive respective corresponding lights obtained when light projected in the plurality of different directions is reflected by the subject, and the control section sets a light receiving range of the plurality of light receiving sections used for calculation of the distance measurement information by the second calculating section to be narrower than a light receiving range of plurality of light receiving sections used for calculation of the distance measurement information by the first calculating section.
Preferably, the camera according to the first aspect comprises a taking lens, and a focal-distance detecting section that detects a focal distance of the taking lens, and the control section switches the light receiving range of the light receiving section used for calculation of the distance measurement information by the second calculating section, depending on the focal distance detected by the focal-distance detecting section.
Specifically, the control section sets the light receiving range of the light receiving section used for distance measurement by the second calculating section to a narrower range as the focal distance detected by the focal-distance detecting section increases.
In a preferred form of the present invention, there is provided a camera comprising a plurality of projecting sections arranged so as to project spot-shaped lights in a plurality of directions for left and right portions of a subject and in one direction for a central portion thereof, a light receiving section comprising a plurality of photoelectric converting elements, the light receiving section being arranged to receive lights reflected from the subject when the lights are projected on the subject by the plurality of projecting sections, a first calculating section that calculates distance measurement information based on outputs from the light receiving section receiving reflected lights from the subject, by driving the projecting sections to project the lights, a second calculating section that calculates distance measurement information based on outputs from the light receiving section receiving extraneous light reflected from the subject, without driving the projecting sections, and a control section that sets a light receiving range of the light receiving section used for calculation of the distance measurement information by the second calculating section to be narrower than a light receiving range of the light receiving section used for calculation of the distance measurement information by the first calculating section.
Preferably, the plurality of projecting sections comprise a plurality of projecting sections for projecting light in the plurality of directions for the left and right portions of the subject and including at least two first projecting sections arranged to project light onto outer portions of the respective left and right portions of the subject, and at least two second projecting sections arranged to project light onto inner portions of the respective left and right portions of the subject, and wherein the first projecting sections are used if a focal distance that is shorter than a predetermined distance is detected by the focal-distance detecting section, and the second projecting sections are used if a focal distance that is longer than the predetermined distance is detected by the focal-distance detecting section.
Preferably, the camera according to the present invention comprises a third calculating section that calculates final distance measurement information based on the distance measurement information obtained by the first calculating section and the distance measurement information obtained by the second calculating section.
To attain the above objects, the present invention further provides a rangefinder device comprising a projecting section that projects light on a range-finding object, a light receiving section comprising a plurality of photoelectric converting elements, a ranging section that performs an active ranging operation of driving the projecting section and calculating distance measurement information based on an output from the light receiving section receiving light reflected from the range-finding object when the light is projected on the range-finding object by the projecting section, and a passive ranging operation of calculating, without driving the projecting section, distance measurement information based on an output from the light receiving section receiving the light from the range-finding object, and a control section that, during the active ranging operation, causes the ranging section to calculate the distance measurement information based on outputs from an identical range of the photoelectric converting elements even when a focal distance changes within a predetermined range, and, during the passive ranging operation, is operable when the focal distance changes within the predetermined range, for setting a range of the photoelectric converting elements used for calculation of the distance measurement information to a narrower range if the focal distance is set to a first value than if the focal distance is set to a second value which is shorter than the first value.
In a preferred form of the present invention, there is provided a rangefinder device comprising a projecting section that projects light in a plurality of directions corresponding to central, right, and left portions of a screen, a light receiving section comprising a plurality of photoelectric converting elements for receiving lights reflected from range-finding objects when the light is projected in the plurality of directions, a ranging section that performs an active ranging operation of calculating first distance measurement information based on outputs from a range of the photoelectric converting elements of the light receiving section that receive reflected light resulting from projection of light in the direction corresponding to the central portion of the screen when the projecting section is driven, calculating second distance measurement information based on outputs from a range of the photoelectric converting elements of the light receiving section that receive reflected light resulting from projection of light in the direction corresponding to the right portion of the screen when the projecting section is driven, and calculating third distance measurement information based on outputs from a range of the photoelectric converting elements of the light receiving section that receive reflected light resulting from projection of light in the direction corresponding to the left portion of the screen when the projecting section is driven, and a passive ranging operation of calculating fourth distance measurement information based on outputs from a range of the photoelectric converting elements of the light receiving section that receive light reflected from the range-finding object corresponding to the central portion of the screen, calculating fifth distance measurement information based on outputs from a range of the photoelectric converting elements of the light receiving section that receive light reflected from the range-finding object corresponding to the right portion of the screen, and calculating sixth distance measurement information based on outputs from a range of the photoelectric converting elements of the light receiving section that receive light reflected from the range-finding object corresponding to the left of the screen, and a control section that, during the active ranging operation, applies an identical range of the photoelectric converting elements for use in calculating at least the second or third distance measurement information obtained from the projection of light in the direction corresponding to the right or left portion of the screen, even when a focal distance changes within a predetermined range, and, during the passive ranging operation, shifts the range of the photoelectric converting elements for use in calculating at least the fifth or sixth distance measurement information in a direction toward the range of the photoelectric converting elements for use in calculating the fourth distance measurement information, when the focal distance is equal to or greater than a predetermined value.
In a more preferred form, the range of the photoelectric converting elements used to calculate the fifth distance measurement information is formed of a plurality of photoelectric converting elements having a first end and a second end, the range of the photoelectric converting elements used to calculate the fourth distance measurement information is formed of a plurality of photoelectric converting elements having a third end located on a side of the second end and a fourth end, and the range of the photoelectric converting elements used to calculate the sixth distance measurement information is formed of a plurality of photoelectric converting elements having a fifth end located on a side of the fourth end and a sixth end, and during the passive ranging operation, the control section shifts the range of the photoelectric converting elements used to calculate the fifth distance measurement information toward the third end or shift the range of the photoelectric converting elements used to calculate the sixth distance measurement information toward the fourth when the focal distance is equal to or greater than the predetermined value.
The ranges of the photoelectric converting elements of the light receiving section used to calculate the distance measurement information on the range-finding objects corresponding to the central, right, and left portions of the screen are formed on an identical light receiving section.
Alternatively, the ranges of the photoelectric converting elements of the light receiving section used to calculate the distance measurement information on the range-finding objects corresponding to the central, right, and left portions of the screen are formed on a plurality of separate light receiving sections.
With the above arrangements of the present invention, in measuring a distance by the calculating means, the distance can be properly measured even if the object to be measured is located at a short distance, while in measuring a distance by the second calculating means, the distance can be measured without causing the conflict between far and near objects.
Furthermore,the rangefinder device and the camera according to the present invention can obtain very accurate distance measurement information using both results of the distance measurements executed by the first and second calculating means.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.